Electronic meters for measuring electric power consumption are rapidly replacing the more traditional electromechanical meters. As the focus towards electronic meters grows, so does the desire to minimize the costs of electronic meters. But the desire to minimize costs is juxtaposed with a desire to add functionality.
An electronic meter typically includes a power supply that receives the AC line voltage as its input and provides a lower voltage DC output (e.g., 5 or 12 volts DC) that is used to power the internal electronic components of the meter. The cost of a meter is proportional to the complexity. of its power supply. Therefore, a simpler power supply helps to lower the cost of the meter. When adding functionality to a meter, the ability of the power supply to support the added functionality can be a factor in the complexity of the power supply design. In addition to the complexity of the power supply, the number of other components needed to support the added functionality also influences the pricing of the meter. Clearly, fewer components in a meter results in a less expensive meter.
One added function presently found in some electronic meters is a remote service disconnect capability. This function allows a utility to transmit a signal to the meter to cause the meter to interrupt the AC line voltage to the customer site. When the meter receives such a signal, circuitry within the meter responds by energizing a relay within the meter that opens the line to the customer to interrupt service. In some electronic meters, the relay is powered by a capacitor within the meter that is charged from the AC line voltage so that, when a service disconnect signal is received, the voltage on the capacitor can be used to energize the relay coil.
Another desirable function included in some electronic meters is power outage signaling. Typically, this function is implemented by circuitry within the meter that detects an outage condition by, for example, monitoring the output of the meter power supply, and then transmits a signal to the utility to report the outage. The outage signal may be transmitted in a variety of ways, such as via telephone modem, power line communications, or wireless transmitter. Obviously, because this circuitry is reporting a power outage, some other source of power is needed to power the transmitting circuitry long enough to enable it to report the outage. One solution is to provide a battery within the meter as a back-up power source. But that solution increases the overall complexity and cost of the meter.
Accordingly, there is a need for new ways to provide power within an electronic meter to support added functionality, such as service disconnect and power outage signaling functionalities, without increasing the overall complexity, and hence cost, of a meter. The present invention satisfies this need.